The GF-1 optical high resolution images have been collected to study mode-2 ISWs of northern Dongsha Atoll in the South China Sea. Based on optical remote sensing images from April to October 2014, mode-2 ISWs spatial distributed in northern Dongsha Atoll, following mode-1 ISWs. Compared with mode-1 ISWs, the crest of mode-2 ISWs was shorter and the length was about 20% to 40% of mode-1. The distance between the positive and negative peaks of mode-2 ISWs was also shorter, the length was about 10% to 50% of mode-1. The fine structure of mode-2 ISWs was investigated by high resolution optical remote sensing images, which offers the references for quantitative study of the energy propagation, fragmentation and dissipation of internal solitary waves.